Ensure `include_source_code` is appropriately passed to the template

Additionally remove the method default to prevent this issue occurring
again.

Changelog: fixed
EE: true

ee/lib/gitlab/llm/completions/explain_vulnerability.rb

@@ -46,7 +46,7 @@ def formatted_error_response(message)
         def response_for(user, vulnerability, options)
           Rails.cache.fetch(cache_key(vulnerability, options), expires_in: 5.minutes, skip_nil: true) do
-            prompt = ai_prompt_class.new(vulnerability, options).to_prompt
+            prompt = ai_prompt_class.new(vulnerability).to_prompt(include_source_code: options[:include_source_code])
             if prompt.to_s.empty?
               formatted_error_response(NULL_PROMPT_ERROR)
             else

ee/lib/gitlab/llm/templates/explain_vulnerability.rb

@@ -34,8 +34,19 @@ def initialize(vulnerability, params = {})
           @params = params
         end
-        def to_prompt(include_source_code: nil)
-          prompt(include_source_code: include_source_code)
+        # This will always provide a prompt by default, but if
+        # `include_source_code` is set true, we'll respond with nil if no
+        # code is available to provide a better interface to the
+        # frontend.
+        def to_prompt(include_source_code:)
+          case include_source_code
+          when true
+            prompt_with_code if eligible_code?
+          when false
+            prompt_without_code
+          else
+            eligible_and_safe_code? ? prompt_with_code : prompt_without_code
+          end
         end
         def presubmission_checks
@@ -52,21 +63,6 @@ def presubmission_checks
         delegate :title, :description, :file, to: :vulnerability
         delegate :source_code?, :vulnerable_code, to: :finding
-        # This will always provide a prompt by default, but if
-        # `include_source_c45ode` is set, we'll respond with nil if no
-        # code is available to provide a better interface to the
-        # frontend.
-        def prompt(include_source_code: false)
-          case include_source_code
-          when true
-            prompt_with_code if eligible_code?
-          when false
-            prompt_without_code
-          else
-            eligible_and_safe_code? ? prompt_with_code : prompt_without_code
-          end
-        end
-
         # rubocop: disable CodeReuse/ActiveRecord
         def identifiers
           finding.identifiers.pluck(:name).join(", ")

ee/spec/lib/gitlab/llm/completions/explain_vulnerability_spec.rb

@@ -3,6 +3,8 @@
 require 'spec_helper'
 RSpec.describe Gitlab::Llm::Completions::ExplainVulnerability, feature_category: :vulnerability_management do
+  using RSpec::Parameterized::TableSyntax
+
   let(:prompt_class) { Gitlab::Llm::Templates::ExplainVulnerability }
   let(:example_answer) { "Sure, ..." }
   let(:example_response) do
@@ -66,12 +68,12 @@
   context 'when a null prompt is returned by the template class' do
     before do
       allow_next_instance_of(prompt_class) do |prompt_class|
-        allow(prompt_class).to receive(:to_prompt).and_return(nil)
+        allow(prompt_class).to receive(:to_prompt).with(include_source_code: true).and_return(nil)
       end
     end
     it 'returns the default error response' do
-      explain.execute(user, vulnerability, {})
+      explain.execute(user, vulnerability, { include_source_code: true })
       expect(GraphqlTriggers).to have_received(:ai_completion_response)
         .with({ user_id: user.to_global_id, resource_id: vulnerability.to_global_id }, hash_including({
@@ -226,6 +228,34 @@
           end
         end
+        context 'when the `include_source_code` option is passed' do
+          where(:include_source_code) do
+            [
+              true,
+              false,
+              nil
+            ]
+          end
+
+          with_them do
+            before do
+              allow_next_instance_of(llm_client) do |client|
+                allow(client).to receive(client_method).once.and_return(example_response[llm_client].to_json)
+              end
+            end
+
+            it 'passes the parameter to the template class appropriately' do
+              expect_next_instance_of(prompt_class) do |instance|
+                expect(instance).to receive(:to_prompt)
+                                     .with(include_source_code: include_source_code)
+                                     .and_call_original
+              end
+
+              explain.execute(user, vulnerability, { include_source_code: include_source_code })
+            end
+          end
+        end
+
         context 'when the `include_source_code` option is toggled' do
           before do
             allow_next_instance_of(llm_client) do |client|